Material CauseMaterial cause is that

Material cause is that out of which something is made, and which remains in it.

Material cause is clearly a sort of cause, for material beings depend on the material they are made out of in order to exist.

something is made: we mean any sort of becoming whatsoever. Material cause is unintelligible apart from this “something”.

and which remains in it: this indicates both that material cause is an intrinsic cause, and that it is different from privation- i.e. a thing can come to be from its opposite, but the opposite does not remain.

Because material cause is necessarily related to the “something that is made”, and something made is clearly an end of making, then all material is for an end. If nature, then, is both material and acts, then nature acts for an end.

Again, because material being relates to something that is made, material cause is constituted by being able to be something. But material cause is real, therefore “being able to be” is real. Potency is therefore real being, although distinguished from being in act. And material cause is potency.

Given that material cause is a sort of potency to be, there is dispute over whether there can be some material cause which is only potency. The classical name for such a material cause is “prime matter”. Note first that material cause taken properly is not repugnant to prime matter, for material cause is properly constituted by its potency, and there is no repugnace for something to be nothing other than that by which it is properly constituted.